What do the following have in common?
Why Bother???
• Exciting subject filled with new discoveries!
• Affects our every day lives!
• Mind blowing ideas that challenge our way of
thinking!
• The wave of the future!
Preview Chapter
The Cosmic Landscape
A Few Definitions
• moon or satellite: a body orbiting a planet.
A Few Definitions
• planet: a celestial body that is in orbit around
the sun, has sufficient mass for its self-gravity
to overcome rigid body forces so that it
assumes a ... nearly round shape, and has
cleared the neighborhood around its orbit.
A Few Definitions
• star: a massive gaseous body held together by
gravity and generally emitting light by nuclear
reactions.
A Few Definitions
• solar-system: A collection of celestial objects
(e.g. planets, comets, asteroids) orbiting
around a common star.
A Few Definitions
• galaxy: A collection of stars, gas, dust, and
dark matter held together by their mutual
gravity.
A Few Definitions
• Universe: Consists of everything around us
Includes
Everything!
Concept Question
Which one of the following is listed in the
correct order from smallest to largest in size?
A) star, planet, solar-system, galaxy, Universe
B) planet, star, solar-system, Universe, galaxy
C) star, planet, galaxy, solar-system, Universe
D) planet, star, solar-system, galaxy, Universe
Scientific Method
• observe
• hypothesize
• test
• modify,reject,or theorize
Mystery Image
Science and PseudoScience
Science and PseudoScience
Science and PseudoScience
Science and PseudoScience
Astrology or Astronomy?
• Uses the positions of planets to predict human
behavior
• Is a branch of Physics
• Uses the scientific method to interpret
observations
• Is considered a pseudoscience
• A detailed study of all the celestial bodies in the
Universe, including planets, moons, stars,
galaxies, etc.
• Associates the signs of the zodiac with personality
traits
Timeline of the Universe
Scientific Notation
• express very small or very
large numbers in powers of ten
• Format: •
.•
X 10•
1.0= 1.0 X 100 (100)
100.0= 1.0 X 102 (102)
1,000.0= 1.0 X 103 (103)
10,000.0= 1.0 X 104 (104)
100,000.00= 1.0 X 105 (1005)
0.1= 1.0 X 10-1
0.01= 1.0 X 10-2
0.001= 1.0 X 10-3
0.0001= 1.0 X 10-4
0.00001= 1.0 X 10-5
(10-1)
(10-2)
(10-3)
(10-4)
(10-5)
Scientific Notation
Examples:
Average Distance from the Earth to the Sun:
149,600,000.0 km  1.496 X 108 km
Mass of ant:
0.004 g  4 X10-3 g
Concept Question
Write -0.00000315 in scientific notation
A) 3.15 X 10-6
B) 3.15 X 106
C) -3.15 X106
D) -3.15 X 10-6
Concept Question
Write 7.89 X 10-6 in regular format
A) 000007.89
B) 0.00000789
C) 7890000
D) 0.0000789
Astronomical Units
Average Distance from the Earth to the Sun  Astronomical Unit
1 A.U. = 1.5 X 108 km
Distance that light travels in a year  Light Year
speed of light in a vacuum: c = 3 x105 km/s (186,000 mi/s)
so one light second: 3x105 km
and one light year: 9.46x1012 km
more practical to use
Looking Backwards in Time
on a planet orbitting
a distant star
here on Earth
55 light years away
68
2 years
70
years old
old
15 years old
70 years old
Because of the finite speed of light,
we are able to look backwards in time!!!
Astronomical Distance Scales are
Astronomical!
The Moon:
1.3 light seconds away
The Sun:
8.3 light minutes away
Andromeda Galaxy:
2.4 million light years away
Alpha Centauri:
4.2 light years away
Galaxies in the Hubble Deep Field:
as far as billions of light years away
The finite speed of light gives us a fossil record of the history of the Universe!!!!
Astronomical
Distance
Scales are
Astronomical!